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  1.  Home
  2. RPG400-L
  3. January 2005

RE: Suggested Technique

<snip>
In my experience it
is almost always confusing to have additional code after the endsl,  At that
point we have done whatever we intended to do and the subroutine really is
at a logical end.   
</snip>

Unless the code after the endsl should be performed for EVERY "When
block"...why duplicate the code for every block???

Thanks,
Tommy Holden


-----Original Message-----
From: Booth Martin [mailto:booth@xxxxxxxxxxxx]
Sent: Monday, January 31, 2005 3:28 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: Suggested Technique


I have no issue with Leave as an opcode and even use it from time to time. 
I have noticed though that generally after the exfmt mentioned in our
example we almost always have a select loop with the command keys,
validation, and entry choices.  Then we have an endsl.  In my experience it
is almost always confusing to have additional code after the endsl,  At that
point we have done whatever we intended to do and the subroutine really is
at a logical end.   



In other words, it makes my teeth itch when I see code after the endsl, so I
would only rarely face the dilema you mention.

 

---------------------------------

Booth Martin

http://www.martinvt.com

---------------------------------

-------Original Message-------

 

From: RPG programming on the AS400 / iSeries

Date: 01/31/05 15:16:28

To: RPG programming on the AS400 / iSeries

Subject: RE: Suggested Technique

 

Because with DOU you will keep processing until the ENDDO.  Why do all the
processing until the ENDDO when you can just LEAVE?

 

Michael Tobey

Applications Analyst

Foremost Farms USA

mike.tobey@xxxxxxxxxxxxxxxxx

IBM Certified AS/400 RPG IV Developer & RPG IV Programmer

 

 

 

-----Original Message-----

From: Booth Martin [mailto:booth@xxxxxxxxxxxx]

Sent: Monday, January 31, 2005 3:09 PM

To: RPG programming on the AS400 / iSeries

Subject: Re: Suggested Technique

 

 

While I understand the idea of DO *hival coupled with a leave, why not just

say it in the first place, and have a DOU F3 and avoid the extra lines of

coding?  DOU F3 is pretty clear, too, isn't it?

 

 

 

---------------------------------

 

Booth Martin

 

http://www.martinvt.com

 

---------------------------------

 

-------Original Message-------

 

 

 

From: RPG programming on the AS400 / iSeries

 

Date: 01/31/05 15:03:41

 

To: rpg400-l@xxxxxxxxxxxx

 

Subject: Re: Suggested Technique

 

 

 

Hi Alan,

 

 

 

<snip>

 

There are some brilliant programmers here, however, who advocate avoiding

 

use of the "iter" and "leave" op-codes. I find it hard to avoid using them

 

myself, but am still open on that issue.

 

</snip>

 

 

 

Now there's a statement! :-)

 

 

 

I would be VERY interested to hear the reasons why LEAVE and ITER have

 

entered the "Hall of Shame" along with CABxx and GOTO.

 

 

 

Personally, I find them very useful and would need a very, very hard sell to

 

convince me to stop using them. They do not preclude well structured code,

 

they have definite branching end-points, and they do not make code less

 

readable to a developer: All long-standing accusations levelled at CABxx and

 

GOTO.

 

 

 

For example - a classic screen loop:

 

 

 

// Display screen...

 

do *hival

 

 

 

exfmt screen

 

 

 

// If user presses F3, leave screen loop...

 

if F3_pressed

 

leave

 

endif

 

 

 

// Validate user input...

 

validateInput()

 

 

 

// If user enters invalid data, re-display screen, displaying error

 

message...

 

if userEntersInvalidData

 

iter

 

endif

 

 

 

// If user elects to update current valid data, update and leave screen...

 

if F8_update

 

updateData()

 

leave

 

endif

 

 

 

enddo

 

 

 

 

 

For me this code is simple - you can only leave the screen if you press F3

 

or update valid data. How do I know??? There's only two ways to leave the

 

screen - via the two LEAVE op-codes. If the code goes beyond the enddo then

 

F3 or F8 MUST have been pressed. In the case of F8, valid data MUST have

 

been entered. If the user enters invalid data then I force a re-display of

 

the screen (ITER) before any update code is reached - this forms a nice code

 

buffer, beyond which I am assured that the input data is valid.

 

 

 

I also prefer using "do *hival" because I do not want any "implicit" exits

 

of the loop. I want to see the exit strategy EXPLICITLY coded within the

 

screen loop. My time is more precious than the CPU cycle time. If I can

 

read/modify the code faster because there are large marker flags in front of

 

me then my company saves money. It's the old adage - KISS!

 

 

 

Just my preference.

 

 

 

Cheers

 

 

 

Larry Ducie

 

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